Professor of Medicine, The University of Melbourne
Joseph Proietto is affiliated with Novo Nordisk,Eli Lilly, and was associated with Nestle. These companies make products that can be used in obesity treatment. He has been a member of Medical Advisory Boards for these companies.
Welcome to part eight ofThe science behind weight loss, a Conversation series in which we separate the myths about dieting from the realities of exercise and nutrition. Here, Joseph Proietto, Professor of Medicine at the University of Melbourne, explains that once people become obese, their bodies are programmed to regain any weight they manage to lose:
The world is in the midst of an obesity epidemic that’s proving difficult to control. As a result, rates of type 2 diabetes, hypertension, heart disease and obstructive sleep apnoea continue to rise, along with social stigma directed at those who struggle to control their weight.
There is emerging evidence that obesity has a strong genetic basis (where a mutation changes the gene sequence and alters the production of protein) or epigenetic basis (where the sequence is normal but the expression or reading of the gene is altered).
We now know that once a certain genetically determined weight is reached, the body defends it vigorously. This means that although someone with clinical obesity can lose weight and keep it off for a year or two, the weight is likely to be regained in the longer term.
Food and the brain
To understand the physiological defence mechanism of body weight, we first need to review how the body regulates our food intake.
Weight is controlled in the hypothalamus, a small area at the base of the brain, located in the midline, behind the eyes. Within the hypothalamus are nerve cells that, when activated, produce the sensation of hunger.